Semiconductor Device Warpage Control via Die Depopulation
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Solution Overview
Problem
Semiconductor wafers experience warpage or bending after the removal of temporary substrates due to differences in coefficient of thermal expansion (CTE) between semiconductor die and encapsulant, leading to defects and handling issues during subsequent manufacturing steps.
Innovation Solution
The process of die depopulation, where certain areas of the temporary substrate are left devoid of semiconductor die to reduce warpage, by strategically removing semiconductor die from central or specific areas to minimize CTE mismatch and bending stress, thereby reducing warpage and enhancing manufacturing yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If semiconductor die are mounted densely on temporary substrate, then throughput and productivity are improved, but warpage increases due to CTE mismatch
Solution Approach 1:
The temporary substrate is segmented into multiple regions with different die mounting patterns. Central regions have reduced die density or are completely devoid of die, while peripheral regions maintain high die density. This segmentation allows different areas to serve different functions: peripheral regions maximize throughput while central regions minimize warpage stress.
Solution Approach 2:
Different areas of the temporary substrate are assigned different die mounting qualities. The central area has lower die density or no die to reduce CTE mismatch stress, while the peripheral areas have high die density for maximum productivity. This local differentiation resolves the contradiction between overall throughput and local warpage control.
2Manufacturing precision
If die depopulation is applied to reduce warpage, then handling and manufacturing quality are improved, but the number of functional die is reduced
Solution Approach 1:
The substrate is divided into functional zones where central regions are depopulated for warpage control and peripheral regions are fully populated for maximum die output. This segmentation ensures that warpage reduction measures do not compromise overall productivity since the majority of the substrate area remains fully functional.
Solution Approach 2:
Die depopulation is applied selectively only to central regions where it most effectively reduces warpage, while peripheral regions maintain full die density. This localized approach minimizes the impact on total die count while achieving the necessary warpage control for manufacturing precision.
3Ease of manufacture
If uniform die distribution is maintained on temporary substrate, then manufacturing simplicity is preserved, but warpage control becomes difficult
Solution Approach 1:
The manufacturing process is segmented into two simple steps: (1) mount die to peripheral regions and selected central regions, (2) remove substrate. The segmentation of die placement patterns does not complicate the manufacturing process itself, as the same automated mounting equipment and substrate removal procedures are used, maintaining ease of manufacture while enabling warpage control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces warpage of the reconstituted wafer, improving handling and manufacturing processes by adjusting the warpage to acceptable ranges without significant loss of throughput, and maintaining structural rigidity for ease of handling.
Implementation Method 1
differences in CTE of the semiconductor die and encapsulant
Data Source
AI summary
A semiconductor device has a substrate with a plurality of active semiconductor die disposed over a first portion of the substrate and a plurality of non-functional semiconductor die disposed over a second portion of the substrate while leaving a predetermined area of the substrate devoid of the active semiconductor die and non-functional semiconductor die. The predetermined area of the substrate devoid of the active semiconductor die and non-functional semiconductor die includes a central area, checkerboard pattern, linear, or diagonal area of the substrate. The substrate can be a circular shape or rectangular shape. An encapsulant is deposited over the active semiconductor die, non-functional semiconductor die, and substrate. An interconnect structure is formed over the semiconductor die. The absence of active semiconductor die and non-functional semiconductor die from the predetermined areas of the substrate reduces bending stress in that area of the substrate.